MANILA, Philippines (CNN) -- Survivors smashed through windows to flee as dozens perished trapped by fire in one of Manila's worst incidents of mass death in recent years.

A heavily armed man walked into the Resorts World Manila casino in the Philippines capital early Friday, shooting gambling machines and setting fires which resulted in the deaths of 37 people.

Initial relief when police said the incident was not terrorism quickly turned to horror as reports began to emerge of the scores of people found suffocated to death inside the building. Many of those who suffocated are said to be women who took shelter in a hotel bathroom.

Of the 37 victims, management said 13 were employees of the casino while the rest were guests. Police have still yet to identify the bodies of six people, including two employees and four guests.

Their bodies were found on the second floor of the building, spread across the casino area, the hallways and a bathroom, police said. They died due to suffocation from smoke when the suspect deliberately set fire to carpets and tables using gasoline he brought with him. The windows were locked.

The injuries of survivors testified to the terror inside the casino, many were hurt breaking windows and jumping from the second floor to escape the fire and smoke.

Waiting for news

Earlier in the day, friends and family of employees gathered outside the casino building in Pasay City on the southern outskirts of Manila, near the city's international airport.

The mood was tense and emotional, and the delay in releasing a full list of victims' names led many worried family members to search hospitals desperately for news of their relatives.

The road that runs along the front of the building was restricted to emergency vehicles, and those taking away the dead. A ferry line that serviced the casino was also halted.

Thomas Orbos, general manager of the Metro Manila Development Authority (MMDA), reminded people "to be vigilant." He added the authority would instruct shopping malls and hotels to be stricter with their security, and that protocols around incidents such as this would be reviewed.

Heightened security checks were already in place for the main metro line that served Pasay City.

ISIS Claims Responsibility

A statement released by ISIS' Amaq news agency said "Islamic State fighters carried out" the attack.

However, ISIS has not released names or pictures of the alleged "soldiers" who carried out that attack, which they tend to do.

Police had said on multiple occasions that the attack was not related to terrorism, and emphasized that there was only one person not multiple attackers involved.

Philippines government forces are currently fighting ISIS-linked militants on the southern island of Mindanao, where the two sides have been battling for control of the city of Marawi for over a week.